The iambic trimeter derives its name from its essential shape, which is three metrical units (hence trimeter) which are each basically iambic in form. The iambic metron has the following shape (where the x is an anceps, the - is a longum, and the u is a brevis):
Hence, reversing the current running though a wire will have the affect of reversing the direction of the magnetic force at a point some distance away from the wire. The affect that this has on the overall magnetic field depends on the shape of the wire.
An electric field has a force proportional to the amount of electric charge within the field, and the force is in the direction of the electric field. On the other hand, force of the magnetic field is proportional to the electric charge as well, but also takes into account the speed of the moving charge.